An organic EL display has a plurality of organic light emitting elements arranged on a substrate. The organic light emitting element basically has a pixel electrode, an organic light emitting layer and a counter electrode. Holes and electrons form electron-hole pairs in the organic light emitting layer, and function as luminescent exciters such that the organic light emitting layer emits light. Lights emitted from the organic light emitting layer are extracted outside through a transparent electrode of the pixel electrode or counter electrode. This light extraction efficiency is several %, and improvement of the light extraction efficiency is demanded.
To increase the light extraction efficiency, one of the pixel electrode and counter electrode is used as a transparent electrode, and the other one is used as a reflective electrode (see, for example, Patent Literature 1 and Patent Literature 2). This is because lights emitted from the organic light emitting layer are efficiently extracted from the transparent electrode. In this case, part of lights emitted from the organic light emitting layer are emitted toward the transparent electrode, and the other part of lights go toward the reflective electrode and are reflected on the reflective electrode toward the transparent electrode. Consequently, by preventing attenuation of both of light going from the organic light emitting layer to the transparent electrode and light reflected by the reflective electrode toward the transparent electrode, it is possible to increase the light extraction efficiency.
A technique has been reported of arranging a transparent conductive film between a metal electrode which is a reflective electrode and an organic light emitting layer and adjusting an optical distance from an organic light emitting layer to a reflective electrode such that extracted light does not attenuate (see Patent Literature 3, Patent Literature 4 and Patent Literature 5).
Further, a technique is known of forming a function layer (for example, organic light emitting layer) of an organic light emitting element by coating and drying a solution including a material of the function layer. A coating area of the solution is defined by partition walls (banks). For example, a technique has been reported of using fluorine resin for the partition walls (banks) which define the coating area (see Patent Literature 6 and Patent Literature 7). By adequately setting the heights and taper angles of the partition walls, it is necessary to set the thickness of the function layer formed by coating and improve film thickness uniformity.
A shape profile of the function layer formed by coating varies depending on the solute of a solution and the type of solvent, and content ratio of these. For example, when a color filter film of each color of the organic light emitting element is formed by coating, the solute of a solution for coating varies per color. Hence, when the heights and taper angles of the partition walls (banks) are the same, the shape of the color filter film varies per color. Hence, a technique has been reported of increasing film thickness uniformity of color filter films by changing the heights and taper angles of the partition walls (banks) per color of the color filter (see Patent Literature 8).